Some prior hydrogen sensors do not include hydrogen-sensing fibers, because they rely on other technologies. Such hydrogen sensors often do not present the same flexibility as compared with hydrogen sensors that are based on hydrogen-sensing fibers.
Other prior hydrogen sensors include hydrogen-sensing fibers. Such hydrogen sensors present some advantages, notably their ability to be distributed and deported sensing systems, but they are not as reliable and/or flexible. For example, such hydrogen sensors often present one or more of the following drawbacks: hydrogen-presence detection that is too imprecise; hydrogen-presence detection that is unreliable over extended periods; hydrogen-presence detection that presents too long of a response time and/or too much complexity.
For example, International Publication No. WO 2009/154216 A1, which is hereby incorporated by reference in its entirety, discloses a hydrogen-fiber-sensor system in which hydrogen detection is realized via a detection layer at the periphery of an optical fiber containing a platinum catalyst whose refractive index is modified by the presence of hydrogen. This patent publication discloses a complicated and costly optical-fiber structure that requires coating the optical fiber with platinum and tungsten oxide layers.
International Publication No. WO 2009/067671 A1 and its counterpart U.S. Patent Publication No. 2011/0199604, each of which is hereby incorporated by reference in its entirety, disclose a hydrogen-fiber-sensor system in which hydrogen detection is realized via modification of optical-fiber characteristics at one or more wavelengths in the presence of hydrogen. The disclosed hydrogen-fiber-sensor system is unreliable over time and has a long response time, especially in environments in which the temperature can vary greatly and unpredictably, because the phenomenon employed is the irreversible increase of attenuation due to irreversible increase of OH— peak (e.g., at 1380 nanometers).
International Publication No. WO 2003/056313 A1 and its counterpart U.S. Patent Publication No. 2005/0118064, each of which is hereby incorporated by reference in its entirety, disclose an irreversible reaction with a metallic catalyst on a fiber cladding, which increases optical-fiber attenuation. These patent publications disclose a complicated and costly fiber structure that uses a metallic catalyst.
Finally, U.S. Pat. No. 5,153,931, which is hereby incorporated by reference in its entirety, discloses hydrogen-presence detection by hydrogen adsorption on hydrogen-sensing fiber cladding. This patent discloses a hydrogen-sensing optical-fiber structure that is based on hydrogen adsorption of fiber cladding, which can merely detect hydrogen presence without reliably quantifying it.
Accordingly, there is a need for a hydrogen-sensing fiber and a hydrogen sensor that alleviates the foregoing disadvantages.